DISTRIBUTION OF TRKB TYROSINE KINASE IMMUNOREACTIVITY IN THE RAT CENTRAL-NERVOUS-SYSTEM

Recent evidence suggests that trkB tyrosine kinase is a high affinity receptor for brain-derived neurotrophic factor (BDNF). BDNF can act as a survival factor for several neuronal subgroups and its mRNA is dist ributed widely throughout the central nervous system. However, the fun ctional targets of BDNF are poorly defined. We have used immunochemica l and immunohistochemical techniques to determine the regional distrib ution and cellular localization of trkB tyrosine kinase-like immunorea ctivity. The staining pattern indicates that the trkB-like antigen is widely distributed and present within both glia and neurons. Astrocyte s were the most intensively labelled but many neuronal populations wer e also stained. In some regions including brain stem, spinal cord, hip pocampus and diagonal band of Broca, neurons were stained at varying i ntensities. In other areas such as the cortex of the forebrain and amy gdaloid nucleus, the stain was intense but diffuse, preventing positiv e identification of the cell types involved. Immunoblot results indica ted two separate protein bands in all brain and spinal cord regions ex amined, of molecular weights 145 and 85 kDa, respectively. These findi ngs aid the definition of neuronal and glial subpopulations of the cen tral nervous system that may utilize BDNF.